Heavy metals can be present in trace amounts in all types of produced fluids such as hydrocarbon gases and crude oils. The amount can range from below the analytical detection limit to several thousand ppbw (parts per billion by weight) depending on the source.
Methods have been disclosed for in-situ treatment of fluid for heavy metal removal. US Patent Publication No. 2011/0253375 discloses an apparatus and related methods for removing mercury from reservoir effluent by placing materials designed to adsorb mercury into the vicinity of a formation at a downhole location, and letting the reservoir effluent flow through the volume of the adsorbing material. US Patent Publication No. 2012/0073811 discloses a method for mercury removal by injecting a solid sorbent into a wellbore intersecting a subterranean reservoir containing hydrocarbon products.
Production of oil and gas is usually accompanied by the production of water. The produced water may consist of formation water (water present naturally in the reservoir), or water previously injected into the formation. As exploited reservoirs mature, the quantity of water produced increases. Produced water is the largest single fluid stream in exploration and production operations. Every day, U.S. oil and gas producers bring to the surface 60 million barrels of produced water.
There is still a need for improved methods for the removal of heavy metals from produced streams right at the production source, particularly for the removal of mercury.